#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;

signed main(){
	cout<<fixed<<setprecision(10);
	
	int N;
	int SA = 0, SB = 0;
	vector<int> A, B;
	
	cin>>N;
	
	A.resize(N);
	B.resize(N);
	
	for(int i = 0; i < N; i++){
		cin>>A[i];
		SA += A[i];
	}
	
	for(int i = 0; i < N; i++){
		cin>>B[i];
		SB += B[i];
	}
	
	if(N == 2) {
		if(SA == SB) {
			cout<<abs(A[0] - B[0])<<endl;
		} else {
			cout<<-1<<endl;
		}
	} else {
		int con = SA - SB;
		
		
		if(SA >= SB && con%(N-2) == 0) {
			con /= N-2;
			bool flag = true;
			int con2 = 0;
			
			for(int i = 0; i < N; i++){
				A[i] -= con;
			}
			
			for(int i = 0; i < N; i++){
				if(A[i] > B[i]) {
					flag = false;
					break;
				}
				
				if((B[i] - A[i])%2 == 0) {
					con2 += (B[i] - A[i]) / 2;
				} else {
					flag = false;
				}
			} 
			
			if(con2 != con) flag = false;
			
			if(flag) cout<<con<<endl;
			else cout<<-1<<endl;
		} else {
			cout<<-1<<endl;
		}
	}
	
	
	
	return 0;
}